Fixing weak cellular coverage

Bloomberg reports that Sprint is giving away "femtocell towers" to a small number of customers who have weak reception in their homes. These towers act as local cellular stations inside your home; they transmit your calls over your internet connection back to Sprint. They therefore depend on your internet speed; if you have a slow or spotty connection, your calls will not sound very good.

If you can't get one for free, these towers seem to cost around $100 retail, with a $5 monthly charge. You can apparently set it up to route multiple numbers over your connection for an additional charge.